cohen



Patented Aug. 12, 1919.

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ELECTRICAL SIGNALING.

APPLICATION .FILED SEPT. 1. 1916.

Patented Aug. 12, 1919.

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L. COHEN.

ELECTRICAL SIGNALING. APPHCATION FILED SEPT. 1. 1916.

1 ,3 1 3,070. Patented Aug. 12, 1919.

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LOUIS COHEN, OF WASHINGTON, DISTRICT OF COLUMBIA.

ELECTRICAL SIGNALING.

Specification of Letters Patent.

Patented Aug. 12, 1919.

Application filed September 7, 1916. Serial No. 118,829.

To all whom it may concern:

Be it known that I, LoUIs COHEN, a citizen of the United States, residing at Waslr ington, in the District of. Columbia, have invented a certain new and useful Improvement in Electrical Signaling, of which the following is a specification. This invention relates to the art of radio signaling and particularly receiving radio signals, and system for use in practising the same.

The object of the present invention is to eliminate electrostatic disturbances and interferences in the reception of radio signals, and thus improve the clearness and accuracy in radio communication.

In carrying out the invention, the'currents of'the disturbances foreign to the signal desired to be received, are transformed into two currents of substantially equal magnitude and delivered to the indicating device as currents of opposite sign, through two circuits, one of which is rendered opaque to the current of the signal to be received, preferably by introducing into it a loop circuit tuned to the frequency of such current, so that the current of said signal will be delivered only through the other of said circuits. In accomplishing this, there may be employed two vantennae, each with a separate receiving equipment coupled thereto;

or a single antenna with two receiving equipments; or one antenna with one receiving equipment and two separate detector circuits associated with the receiving equipment. In every case, the rectified. currents same indicating device and are so arranged as to produce opposite effects therein. This is accomplished either by the use of two transformers, the primaries of which are separately shunted across the respective detectors, and the secondaries are connected in series with each other and with the indicatingdevic'e, but so arranged as to'have the,

currents in the secondaries oppose each a bodying the nvention, in .WhlCh the two other; or by using differentially wound telephones, the respective windings of which are connected across the detectors, so that the "effect in the telephone will be proportional.

to the difference of the currents. One of the receiving equipments as a whole (where two receiving equipments are arsed) or its detec-,

tion. circuit.

tor circuit, or one of the two detector circuits associated with. a single receiving equipment, is rendered opaque to the frequency of current of the signal desired to be received, by introducing in said circuit, a loop circuit tuned to the frequency of the signal which is desired to be received, which has for currents of that frequency, an effect equivalent to that of a very large resistance,

and consequently permits practically no em-- rent of that frequency to pass through to the telephones; currents of any other frequency are not appreciably affected by the loop circuit. It follows, therefore, that the signals which are desired to be received will affect only one receiving equipment or one detector circuit, as the case may be, namely, the one from which the loop circuit is absent, and theeffects may, therefore, be indicated, in the usual manner, in the telephones or other indicating devices. Currents from interferring signals which are of different frequencies or electrostatic disturbances will not be affected by theloop circuit and, therefore, will deliver currents of the same magnitude to both detectors, and neutralize each others effects in the indicating device. Where two receiving equipments are employed, the loop'circuit-may be either in the detector circuit or the secondary oscillation circuit of the receiving equipment with which it is associated. Or there may be, if desired, a loop circuit in each of said circuits, or more than one loop circuit in either or both of them.

In the accompanying drawings- Figure 1 is a schematic view of a system for carrying out the invention, in which the two receiving equipments are coupled separately to two independent-primaries which are connected in series with each other and with the antenna. Fig. 2 is a view similar to Fig. 1, .showing the loop circuit introduced into the oscilla- Fig. 3 is a schematic view of a system emprimaries to whichthe receiving equipments indicating the differential effect of the two :receiving equipments.

Fig. {i shows another embodiment of the invention in which the antenna and the two branch circuits to which the receiving equipments are coupled, are all separately tuned.

Fig. 5 shows a system in which separate antennae are used.

Fig. 6 shows an embodiment of the inven tion in which a single receiving equipment is employed, with two detector circuits associated with it, one of which contains the loop circuit tuned to the frequency of the signal desired to be received.

In each of the figures, the detectors 7 and 7 maybe of any type of detector usually employed in the reception of radio signals. Also while the couplings 2, 4 and 2, 4, are shown as electromagnetic couplings, for the purpose of illustration, any other known type of coupling, for instance, that disclosed in my United States Letters Patent No. 1,123,098 of December 29, 1914, could be used equally well in the embodiment of this invention. In Figs. 1, 2, 4, 5 and 6, the indicating device is acted on by the currents from the detectors through the transformers 10, 11 and 10', 11, While in Fig. 3, the detector currents actdirectly on difi'erentially wound telephones. It is of. course to be understood that the particular methods illustrated, ofassociating the indicating device in the different embodiments of the invention herein disclosed are not to be taken as limitations but merely as illustrations of some ways in which this element of the systern may be supplied.

In the embodiment of the invention illustrated in Fig. 1, 1 is the antenna, 2 and 2 are two inductance coils which are used as primaries-of transformers and can also be used as loading coils for tuning purposes, 3 is the ground connection of the antenna, 4, 5 and 4, 5 are secondary oscillation circuits consisting of inductance coils 4, 4",,and condensers 5, 5, the coils 4 and 4 being interlinked, electromagnetically, with the coils 2 and 2 respectively. 6, 6 are stopping condensers, and 7, 7 are the detectors. is a loop circuit consisting of inductance 8 and condenser 9, andtheir values are so adjusted as to bring the loop circuit into resonance for the frequency of the current of the signal which is desiredto be received. 10, 11' and 10, 11" are transformers preferably having iron cores, and 12 is the indicating device, which may be telephones ora suitable recording'device.

The operation is as follows: Electromagnetic waves acting on the antenna generate a current in it which passes through the primary coils 2 and 2, and through the transformer action of 2,4 and2, 4 generate currents in the secondary oscillation circuits which affect the detectors 7 and 7 Now 1 I the secondary circuit which has the loop circuit is tuned, hence, if .we adjust the inrent of the signal desired to be received, thesignal has no effect on that circuit, and consequently only manifests itself in the indicating device through the action of the receiver from which the' loop circuit is absent. In other words, we get the same effect as if we only had one receiver coupled to the antenna circuit. Any other signal which may be sent out by nearby stations and of any frequency but different from that of the signals to be received, will act on both receiving equipments. If new the couplings 2, 4 and 2, 4,'or 10, 11 and 10, 11, be so adjusted relatively to each other that the indicating device is acted upon equally by both receiving equipments, and the secondaries 11 and 11 of detector transformers are so connected that the currents generated in them are of opposite sign, then the effect of electrical disturbances due to signals of frequencies different from that of the signal. to be received beconies neutralized and does not manifest itself in the indicating device.

In order to make this system effective for necessary to detune slightly the antenna circuit 1, 2, 2, 3, so that the oscillations generated in it by impulsive disturbances, such as are produced by static, will make the antenna system oscillate with a frequency slightly different from the resonance frequency of the loop circuit 8, 9, and consequently, the currents induced in the secondary circuits will be equally effective in both 4, 5, and 4", 5', and their effects neutralized in the indicating device 12 becauseof the reverse magnetic coupling 10, 11, 10, 11. As illustrated in Fig. 2, the loop circuit 8, 9 may be introduced in the oscillation circuit instead of in the detector circuit.

According to Fig. 3, the two primaries to which the oscillatory circuits are coupled, are joined in parallel. The currents gener'a ted in the antenna divide equally in the said two branches and thus generate currents the same as in the case of Fig. 1 described.

above. As a means for indicating the differenti'al effect of thetwo receiving equipments, a differential telephone is shown in Fig. 3, but the arrangement shown in this figure is of course not limited to use with this particular method indicating" device.

Fig. 4 is a modification of Fig. 3, which of introducing the consists in introducing a loading coil 14 in the antenna, and two condensers 15 and 15 in the two parallel branches. The purpose of these extra elements is to enable one to tune independently the antenna and the two branches. By this means, antenna, 1 and loading coil 14 can be tuned for the frequency of the current of the signal to be received, and also branch 15, 2' is tuned independently to the same frequency; while branch 15, 2 is tuned to a slightly different frequency; so that the current of the signal to be received will pass mostly through branch 15, 2, and very little will be diverted through branch 15, 2. This is desirable, because the energy of the incoming signal is, transmitted to the. indicating device only through the receiving equipment coupled to branch 15, 2, and the signal current flowing in branch 15, 2, is entirely wasted; the loop circuit in the receiving equipment associated with branch 15, 2, does not permit anycurrent of that frequency to pass.

Fig. 5 suggests the use of two independent antennae 1, 1, having independent primary coils 2, 2, to which are coupled the two receiving equipments. The operation is similar to that of Fig, l. The independent antennae may be so closely associated as to be mounted upon the same mast, if desired.

As shown in Fig. 6, the present invention may be realized by the use of a single receiving equipment, provided two detector circuits be associated with it, one of which detector circuits has associated with it, a loop circuit tuned to the frequency of the signal desired to be received.

I claim 1. The method of eliminating effects of foreign electrical disturbances from the indicating devicein the reception of radio sig nals, which consists in transforming the currents of said disturbances into two currents of substantially equal magnitude, delivering them to the indicating device as currents of opposite sign, through two circuits, one of which contains a loop circuit tuned to the frequency of the current desired to be received, and delivering the current of said signal only through theother of said circuits.

2. The improvement in the art of radio signaling which consists in employing two receiving equipments with an indicating device common to both; rendering one receivceivingequipments and oppose their efi'ects I in the indicating device.

3. The improvement in the art of radio signaling which consists in employing two receiving equipments with an indicating device common to both and with a loop circuit, tuned to the frequency of the signal to be received, introduced in the detector circuit ofv one of the receiving equipments, thereby rendering said receiving equipment'opaque to currents of the patricul-ar frequency of the signal to be received, and leaving the other receiving equipment alone affected by the incoming signal, and causing currents of all other frequencies or electrostatic disturbances to afiect both receiving equipments and oppose their effects in the indicating device.

4. A system of radio signaling comprising two receiving equipments separately related to a suitable antenna through means of oscillation transformers, a loop circuit embodied in one receiving equipment adapted to be tuned to current frequency of a signal to be received, and an indicating device common to both receiving equipments.

The foregoing specification signed at Washington, District of Columbia, this 6th day of September, 1916.

LOUIS COHEN. 

